If one or both footwell blowers short out you will blow one of the 2 fuses shown in RED in the schematic below. If you are in speed #3 (hi speed) you will blow the fuse on the left. If in speed #1 or Speed #2 (low or medium speed) you will blow the fuse on the right.
Trouble is that those 2 fuses are way down stream from the blowers and a shorted blower could compromise other components like the 'Heat Controller' (low and med speed) or the 'Aux Blower Relay' (hi speed). So it would not be a bad idea to place inline fuses right at each blower motor. Never gave this to much thought but I like the idea.